LRTK-changing 3D Surveying: High Precision at Low Cost, No Specialist Operator Needed

In recent years, advances in surveying technology have made advanced 3D surveying, once handled only by specialist surveyors, increasingly accessible. Techniques that convert terrain and structures into complete three-dimensional data using drones and laser scanners have emerged and attracted attention in construction and infrastructure fields. However, there remain persistent concerns such as “expensive equipment and skilled operators are required” and “difficult to master,” which prevent some sites from adopting the latest technologies.

Enter LRTK, a new approach that combines smartphones with satellite positioning technology. LRTK is an innovative surveying tool that turns a smartphone into a centimeter-level positioning device simply by attaching a pocket-sized RTK-GNSS receiver. It can be used easily by anyone without a specialist operator, and its combination of high accuracy and low cost is expected to dramatically lower the barrier to 3D surveying. This article explains the basics of 3D surveying, compares conventional methods, and describes the new surveying approach enabled by LRTK born from the wave of digital transformation (DX). We will introduce LRTK’s new surveying paradigm, practicality, and benefits through use cases in construction sites, infrastructure maintenance, and urban planning.

What is 3D surveying

As the name implies, 3D surveying measures objects in three directions—length, width, and height—and acquires data as three-dimensional information. By recording terrain, buildings, and structures as three-dimensional coordinates (X, Y, Z), complex shapes that are difficult to grasp on traditional 2D plans can be accurately reproduced. For example, point cloud data (a collection of many measured points) obtained by scanning objects with laser or cameras can digitally visualize rock surface irregularities and building details. Many 3D surveys are performed as non-contact measurements from a distance without directly touching the object, making them suitable for measuring steep terrain or large structures that are difficult for people to enter. In recent years, initiatives promoted by the Ministry of Land, Infrastructure, Transport and Tourism such as *i-Construction* have accelerated adoption, and 3D surveying is becoming a standard technology in civil engineering and construction. Demand for 3D data use is increasing across a wide range of fields—from on-site as-built management to design and construction planning, and even maintenance and the creation of digital twins for urban infrastructure.

Conventional surveying methods and challenges

The main methods traditionally used to obtain 3D survey data include the following. Each has advantages but also faces issues in terms of cost, effort, and required expertise.

• Total station surveying: This method uses a total station (TS), an optical distance-measuring instrument, to measure angles and distances at multiple points one by one to calculate coordinates. While it achieves millimeter-level accuracy and is highly reliable, it measures point by point, so surveying a wide area requires considerable time and effort. It is a traditional method that relies heavily on manual labor and careful operation by a skilled operator.

• Drone photogrammetry: A camera-equipped small unmanned aerial vehicle (drone) captures numerous photos of the ground from the air, and software reconstructs the three-dimensional shape. UAV photogrammetry is revolutionary in that it can survey areas such as forests or large development sites that people cannot enter, in a short time from the air, and has spread rapidly in recent years. However, drone flights require compliance with aviation laws and piloting skills, and operations are restricted in urban areas or bad weather. The processing to generate models from photos takes time, and improving accuracy requires extra work such as setting ground control points (GCPs).

• Terrestrial laser scanner surveying: This method uses a 3D laser scanner mounted on the ground and rotates it to densely scan surrounding structures and terrain. Laser scanners can acquire hundreds of thousands to millions of points in a point cloud, producing highly detailed 3D data. The precision is high and useful for as-built management or structural displacement measurement, but the equipment is large and expensive—costing several million to tens of millions of yen—and transport and setup are time-consuming. Raw data also contains noise, so specialized work such as noise removal and integration of multiple scans with dedicated software is indispensable.

• GNSS surveying (RTK): This method uses satellite positioning systems like GPS to determine position coordinates on Earth. The RTK (real-time kinematic) method corrects errors by simultaneous observation with a base station and a rover, enabling real-time positioning at centimeter-level accuracy. Traditionally, high-precision GNSS surveying required expensive dedicated receivers and communication devices, and it was common to outsource to surveying companies or have skilled personnel operate the equipment. The results were also limited to individual point coordinates, so capturing whole surfaces or volumes required many point measurements or combining with other methods.

As described above, conventional 3D surveying methods each had trade-offs. High-precision surveying essentially required expensive dedicated equipment and specialized skills, making adoption difficult for site engineers. Many sites faced the dilemma of “not being able to measure a needed location immediately” or “data processing and sharing taking too long.”

Progress of DX in surveying

Recently, DX (digital transformation) has been emphasized across the construction industry, and digital technologies are rapidly spreading to surveying sites. Initiatives represented by the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* and “smart construction” are accelerating efforts to dramatically improve productivity using ICT. In surveying, moves to digitize tasks that previously relied on tapes, levels, and total stations—manual and labor-intensive work—using digital devices have gained momentum.

Site DX brings various benefits to surveying work. Digitizing manual tasks can help address labor shortages and reduce human error, and results previously recorded on paper drawings or logs can be shared instantly in the cloud. For example, in the past, measurements taken on-site were handwritten and later transcribed into drawings or reports back at the office. By adopting DX, measurements are automatically recorded and calculated as electronic data in real time, and photos are saved with location information, so recording work is greatly reduced. In addition, on-site data can be shared in real time with supervisors and clients in the office, allowing as-built conditions to be checked and instructions given remotely. Smoother data integration enables quicker corrective actions if problems arise, accelerating the PDCA cycle of construction management and enabling early detection and correction of quality issues. In this way, digital technology is transforming surveying itself and contributing to overall improvements in site productivity and quality.

Features of surveying with LRTK

LRTK is a smartphone-mounted high-precision positioning system developed by a startup originating from the Tokyo Institute of Technology. A small device weighing about 125 g and about 13 mm thick attaches to a commercial iPhone or iPad with one touch; launching the dedicated app turns the smartphone into a centimeter-accuracy surveying instrument. No complex setup is required: the current position is displayed in real time on the smartphone screen, and you can record survey points or plot them on maps and drawings on the spot while viewing your location. The revolutionary aspect is that high-precision surveying that used to require specialized equipment and skilled operators can now be performed easily by anyone on site.

Main features of LRTK surveying:

• Centimeter-level precision: Using GNSS real-time correction technology (RTK), positions can be measured with errors on the order of centimeters. Ordinary smartphone GPS has errors of several meters, but LRTK receives correction data from a base station and computes positions on the smartphone, dramatically improving positioning accuracy. This precision is sufficient to meet advanced civil engineering and surveying needs such as as-built management and checking deviations from design lines.

• Easy operation without specialist knowledge: The smartphone app’s interface is designed so you can record points and take photos by simply following on-screen buttons. Non-surveyors such as site supervisors and inspection staff can handle it intuitively, and guidance functions help prevent measurement mistakes. For example, when you take a photo, latitude, longitude, and orientation are automatically recorded and saved and shared with notes. There is no need to operate multiple devices or record information by hand—anyone can achieve “press-only surveying”.

• Real-time positioning and instant sharing: With LRTK, measured data is not only recorded on the smartphone but can be uploaded to the cloud—LRTK Cloud—with one tap via mobile or satellite communications. managers in the office can immediately check measurement results in a web browser and download CSV or drawing data. This shortens the time from measurement to reporting and facilitates information sharing with remote locations. Even in areas without cellular coverage, LRTK supports the centimeter-level augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite Michibiki, enabling continued high-precision positioning without internet access.

• Compact, lightweight, and highly mobile: The LRTK device, integrated with a smartphone, is pocket-sized, so workers can carry it at all times and measure whenever needed. Unlike traditional equipment, there is no need to transport heavy machinery or set up tripods; one person can walk the site and take measurements. For example, attaching LRTK to a helmet allows continuous positioning while moving hands-free, making it possible to easily acquire wide-area terrain data.

• All-in-one multifunctionality: LRTK does more than just measure positions; it consolidates various on-site measurement functions into a single smartphone. In addition to point coordinate measurements, it can record longitudinal and cross-sectional ground profiles by continuous measurements at set intervals, overlay design models on the real scene using AR (augmented reality), and guide layout/staking-out (marking) tasks. Combined with an iPhone’s LiDAR scanner, it can perform high-density 3D measurements by scanning the surrounding environment as a point cloud while assigning global coordinates to all points. Tasks that previously required dedicated surveying instruments or expensive 3D scanners can be completed with just LRTK and a smartphone, greatly streamlining on-site equipment.

• Low-cost adoption: LRTK’s significantly lower adoption cost compared to conventional surveying equipment is another attractive point. Because it leverages existing smartphones, the only necessities are the small GNSS receiver (LRTK device) and software subscription. You can start high-precision surveying from the scale of a few hundred thousand yen, without purchasing laser scanners or dedicated equipment costing several million yen, making one-per-person deployment realistic. This resolves the issue of “not being able to measure when needed due to limited equipment” and makes it easier to ensure measurements can be taken at the required times.

Actual use cases of LRTK

Use in construction sites

On construction sites, LRTK dramatically improves efficiency for as-built measurement and layout/marking tasks. For example, in road construction, it used to be necessary to wait for a surveying team to confirm heights after concrete placement or measure slope gradients. With LRTK, site supervisors and workers can measure pavement elevations on the spot and immediately confirm whether they match the design. Measurement results are shared via the cloud with office engineers, allowing remote real-time checks and immediate instructions if problems are found. Eliminating waiting for surveying increases productivity as workers can perform self-measurement during construction.

LRTK is also effective for structure layout (staking/marking). By checking design coordinates on site, workers can perform piling or foundation placement accurately by themselves, making tasks that previously required two people with a total station possible for a single person. In earthworks, volumes of completed fills and cuts can be calculated immediately from point cloud data measured with LRTK. Moreover, during rebar inspections or buried-object checks, simply taking photos with an LRTK-equipped smartphone saves records with date, latitude, and longitude, greatly improving the reliability of evidence compared to the conventional method of photographing a handwritten board. Improved quality control and progress management on site, and automated generation of measurement reports, reduce the burden on site supervisors and speed up construction.

Use in infrastructure maintenance

LRTK is also useful for maintenance of existing infrastructure such as bridges, tunnels, and roads. During routine inspections, inspectors can record the location of cracks and defects precisely with latitude and longitude simply by photographing the structure with an LRTK-equipped smartphone. Items that were previously marked manually on inspection drawings can be digitally recorded with one tap, eliminating later comparison effort with drawings and simplifying longitudinal comparisons. LRTK is also powerful for measuring high or hazardous locations. Using LRTK’s object-positioning feature, coordinates of points such as the top of a bridge pier or a spot on a steep slope that cannot be reached by hand can be measured remotely through the camera. This non-contact ability to pinpoint locations inaccessible to people reduces the need for scaffolding or working at height, improving inspection safety.

Furthermore, LRTK is useful for assessing damage immediately after natural disasters. In sites where roads have collapsed due to earthquakes or heavy rain, pocket-sized LRTK can be attached to a helmet for on-foot surveys. Even in areas where cellular communications are down, satellite augmentation signals allow standalone positioning, so accurate coordinates and extents of damaged areas can be recorded on site and shared quickly via the cloud later. The ability to conduct initial surveys immediately without waiting for large survey vehicles or personnel is a major advantage. Due to this flexibility, LRTK is gaining attention as a new tool for infrastructure maintenance and disaster response.

Use in urban planning

LRTK is also effective in urban spatial data development and city planning. In urban areas where drone flights are restricted and surveying is difficult, LRTK enables measurement of streets and building layouts while walking, and reflecting them in 3D models and maps. For example, municipal staff using LRTK to巡回測定 roads signs, utility poles, and block boundaries can efficiently develop detailed urban infrastructure GIS data. Surveys that previously required outsourcing can now be frequently conducted in-house, keeping current-condition data fresh for urban planning. LRTK surveying can also be applied to 3D recording of historic buildings and cultural assets. Because it enables easy creation of high-precision digital archives, it can contribute to future urban development and the preservation and utilization of tourist resources. In addition, as part of smart city initiatives, real-time urban data acquired by LRTK plays a key role in building urban digital twins—digital replicas of physical spaces. Such uses in urban planning will support more accurate and flexible decision making for city development.

The new face of surveying brought by LRTK

The arrival of LRTK is starting to change the very nature of surveying. High-precision surveying can now be practiced “by anyone, anywhere, anytime,” and surveying is no longer the exclusive domain of a few specialists but is being democratized as a basic on-site tool. This enables smoother construction processes that previously stalled while waiting for surveys, allowing immediate measurement and confirmation when needed and facilitating flow-based workflows to progress to the next task. Real-time information sharing between sites, headquarters, and clients makes geographically distributed team-based construction possible. As data accumulates, we can expect advances toward data-driven management such as trend analysis of as-built conditions and enhanced quality control.

Moreover, if one LRTK per person becomes common, the environment of being able to “measure whenever needed” will become the norm, ensuring on-site decisions are always based on the latest data. This is also effective for safety management, enabling quick responses to subtle ground subsidence or structural displacement. With a shortage of experienced surveyors, empowering on-site staff to perform surveying themselves helps bridge the gap in technical succession and move toward less person-dependent operations. The combination of ease of use and high precision offered by LRTK aligns with the philosophy of *i-Construction* promoted by the Ministry of Land, Infrastructure, Transport and Tourism and can be seen as a next-generation solution supporting industry-wide DX in construction. The emerging new surveying style enabled by LRTK is expected to spread to many more sites and bring a revolution in both operational efficiency and quality.

Conclusion

LRTK, which is both highly accurate and easy to use, is truly a trump card for lowering the barrier to on-site surveying. As outlined above, its practicality as a simple surveying tool usable by anyone is being proven, and the efficiency and labor-saving benefits of adoption are immense. Freeing sites from cumbersome surveying tasks and moving toward construction management based on real-time accurate data represents a major revolution for the field. By leveraging LRTK, it will be possible to pursue productivity and quality together with flexible thinking that breaks free from conventional norms. Embracing the latest technologies and starting DX through simple surveying can be the first step to bringing new value and competitiveness to sites. Now is the time to experience firsthand the practical benefits LRTK can bring to your site, without being bound by traditional methods.